Spring drive system and window cover

Abstract

A spring drive system useful for window covers is disclosed, which comprises one or more coil spring drives or flat spring drives and the combination whose elements are selected from one or more of a group which includes (1) a band or cord transmission which provides varying ratio power transfer as the cover is opened and closed; (2) gear means comprising various gear sets which provide frictional holding force and fixed power transfer ratios; (3) a gear transmission which provides fixed ratio power transfer as the cover is opened or closed; (4) crank mechanisms; (5) brake mechanisms; and (6) recoiler mechanisms. The combination permits the spring drive force to be tailored to the weight and/or compression characteristics of an associated window cover such as a horizontal slat or pleated or box blind as the cover is opened and closed.

1 . A spring drive unit comprising: a base; a rotatable shaft mounted to the base; a spring mounted to the base and having a fixed end and a rotatable end; and a gear transmission of given drive ratio between two gears thereof, operatively connected at a first one of the two gears to the rotatable end of the spring and operatively connected at a second one of the two gears to the rotatable shaft, thereby applying the given drive ratio between the spring and the shaft for altering the force applied between the shaft and the spring and for altering the ratio of the shaft rotating speed to the spring rotating speed.  
   
   
       2 . (canceled)  
   
   
       3 . The spring drive unit of  claim 1 , wherein the spring is a flat spiral spring.  
   
   
       4 . The spring drive unit of  claim 1 , further comprising: a band transmission of varying drive ratio between two gears thereof, operatively connected at a first one of the two gears to the rotatable end of the spring and operatively connected at a second one of the two gears to the shaft, thereby applying the varying drive ratio between the spring and the shaft for varying the force applied between the shaft and the spring and for varying the ratio of the shaft rotating speed to the spring rotating speed.  
   
   
       5 . (canceled)  
   
   
       6 . The spring drive unit of  claim 4 , wherein the spring is a flat spiral spring.  
   
   
       7 - 9 . (canceled)  
   
   
       10 . A window cover system of the type comprising: a base; an extendible window cover; and lift means including lift cords attached to the cover for raising and lowering the window cover to selected positions, the improvement comprising: 
 a spring drive unit connected to the lift cords for assisting the raising and lowering of the cover to selected positions, the spring drive unit comprising a spring mounted to the base and having a fixed end and a rotatable end; and a gear transmission of fixed drive ratio; the gear transmission operatively connected at one end to the rotatable end of the spring and operatively connected at the opposite end to the lift means, thereby applying the fixed ratio between the spring and the lift cords, for altering the ratio of the distance traversed by the cover to the distance traversed by the rotatable end of the spring and for altering the force applied between the cover and the spring; and    the gear transmission having inherent friction opposing movement of the lift cord-supported cover and thereby tending to maintain the cover at the selected positions.    
   
   
       11 . (canceled)  
   
   
       12 . The spring drive unit of  claim 10 , wherein the spring is a flat spiral spring.  
   
   
       13 . The spring drive unit of  claim 10 , further comprising: a band transmission of substantially continuously varying drive ratio, operatively connected at one end to the rotatable end of the spring and operatively connected at the opposite end to the lift means, thereby applying the substantially continuously varying drive ratio between the spring and the lift cords for substantially continuously varying the ratio of the distance traversed by the cover to the distance traversed by the rotatable end of the spring and for substantially continuously varying the force applied between the cover and the spring.  
   
   
       14 . (canceled)  
   
   
       15 . The spring drive unit of  claim 13 , wherein the spring is a flat spiral spring.  
   
   
       16 - 51 . (canceled)  
   
   
       52 . A window cover system comprising: 
 an extendible window cover; a housing; lift cords attached to the cover and wrapped around pulleys mounted to the housing for raising and lowering the extendible cover; and    a spring drive system connected to the lift cords for assisting the raising and lowering of the cover; the spring drive system comprising:    a shaft mounted to the housing, a spring drive comprising at least one substantially flat spring; the spring drive being mounted to the housing and having a storage end and an output end, the spring drive having a non-constant torque or force as the cover is extended and retracted, and a bevel gear set having one gear connected to the spring output end and a second gear operatively connected to the shaft for rotating the lift cord pulleys, the spring drive thereby applying the torque or force to the cover and the spring drive having inherent inertia maintaining the position of the cover.    
   
   
       53 . The window cover system of  claim 52 , further comprising: a gear transmission of fixed drive ratio and having first and second ends; the second gear connecting the first end of the gear transmission to the rotatable end of the spring drive; and the second end of the gear transmission being connected to the shaft for rotating the lift cord pulleys, the gear transmission thereby applying the fixed ratio between the spring drive and the lift cords, determining the ratio of the cover travel distance to the winding distance of the substantially flat spring and controlling the force applied to the cover by the spring drive, and applying the inherent inertia thereof to the lift cord pulleys for maintaining the position of the cover.